Radiocommunication



Aug. 23 1923. 11,465,357, R. A. HEISING RADIOCOMM-UNICATION Filed Sent. 27, 1919 Raymond/1. Has/27 EH STATES PATIENT @FFHQEO RAYMOND A. HEISING, OF EAST ORANGE, ELECTRIC COMPANY INCORPORATED, OF

NEW YORK.

NEW JERSEY, ASBIGNOR TO WESTERN NEW YORK, N. Y., A CORPORATION 035' RADIOCOMMUNICATION.

Application filed September 27, 1919. Serial No. 328,909.

To all whom it may comm:

Be it known that I, RAYMOND A. HEISING, a citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Radiocommuni-.

cation, of which the following is a full, clear, concise, and exact description.

The present invention relates to signaling by means of high frequency waves.

More particularly, the invention relates to radio signaling and to method and means for facilitating the transmission and reception of more than one radio message at the same time.

In wire transmission systems a message carried on one line for the most part has no effect upon a message carried at the same time upon another line and by providing enough lines between any two points, any

number of messages or conversations may be in progress at the same time between these points. In radio signaling, however, in which the waves are unguided the number of messages that can be sent and received at once between neighboring stations is dependent upon some characteristic difference between the transmitted waves which will enable one wave to be separately receivedfrom all the others. This places a limitaq tion upon the number of messages that may in practice be thrown uponthe ether at the same time, but it is to be noted that the limitation is not that of the natural media to transmit,but is that of the receivers each to receive the particular wave intended for it.

It is an object of the present invention to increase the number of messages that can be separately sent and received by radio at the same time. The invention is concerned especially with increasing the number of conversations that can be carried on simultaneously by radio between communicating stations and in this sense may be considered as an improvement upon the system disclosed in my application, Serial No. 81,980, filed March 3, 1916, the subject matter of which is described in French Patent No. 505,106, granted April 20, 1920. a

The invention will be described with particular reference to receiving means and method since transmitters of known type may be used in the present system and 1n fact the wave to be received at a given station may be accompanied by a great number of other waves over which the transmitter of the present system has no control, but which may emanate from as many different sources as there are waves being transmitted.

In the so-called heterodyne reception a locally produced wave of radio frequency ls caused to interact with the incoming signal wave to produce an audible frequency wave from which the signal can be read. This method has long been in use in telegraphy for receiving a single message at a time. The sowcalled heterodyne reception is to be distinguished from the present invention. however, in which greatly increased selectivity is obtained for radio telephony over devices heretofore known or used. The problem here is not to render an undamped wave audible in a telephone receiver by causing production of beats as is the case where the so-called heterodyne is used. It is to be noted that a voice-modulated wave on the contrary acts at the receiver like a damped wave and may be received with a crystal detector directly. The present invention rather seeks to increase the selectivity of the receiver for a telephone modulated or other radio wave so that it can be received exclusively of other waves which may be of such closely neighboring frequencies that simple tuned circuits could not possibly separate them. This is accomplished according to the present invention by causing the incoming waves to interact at the receiver with a wave which is preferably produced locally, and which is of such frequency that resultant high frequency waves are produced of the sort employed in carrier current telephony on lines. The effect of this is to reduce the frequency of the speech modulated wave, which wave, however, is still inaudible, but may be readily selected and afterward detected to obtain the speech component. By this method radio waves which differ in frequency by only one or two per cent have their frequency stepped down by the same amount so that, for instance, the frequency of one of the waves this process in no way affects the message, but the wave resulting from the interaction between the received waves and the locally produced Wave is still a modulated wave which must be detected to be received.

In the drawing, Fig. 1 shows a transmitting arrangement that is adapted for use in the system according to the present invention, and Figs. 2 and 3 illustrate receiving arrangements.

Since a receiving system according to the invention is particularly adapted for use in amultiplex radiosystem, a transmitter has been shown in Fig. 1 of a type adapted.v

for use in such a multiplex system. The antenna 1 is supplied with two voice-modulated radio frequency waves through the amplifier A from the oscillator-modulator sets T and T Other similar sets employing different frequencies from those of the sets shown may be provided as desired. Except for their frequencies, the sets T and T may be alike and only set T need be described therefor. oscillator 2 of well-known construction, the frequency of which may be controlled by the variable condenser 3, and the modulator 4 which is shown connected in a well-known manner to control the output wave from oscillator 2. The thermionic discharge devices 2 and 4 may be of well-known construction, and where one such device is shown there may be several connected preferably in parallel to increase the power output. Space current is supplied to the plates or anodes of both devices 2 and 4' from the 1 source 5 through the low frequency choke coil 6, and included in the circuit leading to the anode of device 2 is the high freuency choke coil 7 The impedance of the device 4 is controlled by the potential of the third or grid electrode 8 and the po-' tential may be controlled from the circuit 9, which includes the microphone 10 and a source of current, as shown, and is coupled with the grid circuit f the device 4. When speech waves are directed against microphone 10, the impedance of device 4 to the passage of current is varied in accordance with the speech waves and the output of the oscillator 2 is varied in a similar manner. The wave so produced and controlled is transmitted through the coupling 11, is

amplified by the amplifying devices at A and is impressed upon transmitting antenna 1. A similarly controlled radio frequency wave of different frequency is transmitted from the set T through the coupling 13 and is impressed upon the same antenna 1.

The wave from the set T, is controlled by the microphone 12. In the system according to the present invention, the frequencies of the sets T and T may be relatively very close together.

Fig. 2 shows a receiving circuit for selec- This set comprises antively receiving a single radio telephone message or other radio message exclusively of others which may be in the process of transmission through the natural media at the same time. The articular arrangement of Fi 2 is not strictly a multiplex receiver, there ore, since it is adapted to receive one message only at a time. The receiving antenna 15 and the circuit 16 coupled to it are brought into resonance with the wave that is to be received. Connected across the terminals of the circuit- 16 is the detector 18 which may be of well-known construction and is shown as a three element discharge device. Also coupled to the antenna 15 or circuit 16 is a local source 17 of any suitable type for generating a radio frequency wave, and the degree of coupling of the oscillator 17 with the antenna as well as the coupling between 15 and 16 are indicated as being adjustable. The frequency of source 17 is different from that of the wave to be received and the output of the detector 18, therefore, contains as a component a combination frequency which is the difference-frequency between the received wave and the wave from the source 17. This component will in general be readily selectable from other components produced-in the output of the detector 18, and for receiving this difference frequency the circuit 19 is provided and made resonant to the difference frequency. Coupled 22. By thus reducing the frequency of the speech-controlled wave from the transmitted radio frequency to the comparatively low difference frequency to which circuit '19 is tuned, the incoming wave may easily be distinguished from other waves of nearly the same frequency.

The receivmg arrangement of Fig. 3 is suitable for use in a multiplex radio telephone system in which the transmitting station may be of the type shown in Fig. 1. Fig. 3 contains the elements 15, 16, 17 and 18 as Fig. 2, but the output circuit of the detector 18 contains, instead of one resonant circuit, a plurality'of resonant circuits 23, 23, etc., one for each speech modulated wave that is to be se arately received. The

device 18 thus constitutes a detector or demodulator common to the several radio frequencies which are to be received. Also there is a separate second detector for each wave to be received indicated at 27 28, etc.

, obtainable by memes? Each such detector is associated with the appropriate circuit 23, 24, etc., through the medium of tuned circuits 25, 26, etc., and has in its output circuit a receiver 29, 30, etc., one for each of the messages that are to be received simultaneously. It will be noted that in the system of F 1g. 3, one local source 17 and one detector 18 serve for all of the waves to be received simultaneously.

As an example of the increased selectivity the use of the present invention, the following numerical considerations may be noted. If one radio station is transmitting telephonically on a carrier frequency of 650,000 cycles and a-second at 640,000 cycles, no simple radio receiver can separate them. With this system a local frequency of 600,000 cycles will produce a 50,000 cycle difference frequency with one wave and 40,000 cycles with the other wave. By means of the second set of tuned circuits 23, 24, etc., these difference frequencies or intermediate frequencies are easily separated. The system thus allows a separate conversation to be had for each 10,000 cycle step in the frequency range, tend from a few thousand der of millions of cycles. the increased possibilities consider the best wave len th range for medium distance communication, 600 meters to 1500 meters inclusive. At present this range is being used for five conversations only. By the system of the present invention using sustained waves, the same range will accommodate 30 conversations. From 300 to 600 meters inclusive are now being secured four cycles to the orconversations. By the system of this invention the same range will give fifty conversations. This computation is based on a fixed frequency-difference of 10,000 cycles, although by accurate setting of wave lengths and the use of filters it could probably be reduced to a conversationfor each 6,000 cycles, which would means an increase still further of 66% in the number of conversatie'ss over those above given.

As a... instance of the adaptability of the system of the present invention, the circuit arrangement. of Fig. 2 may be assumed to be a receiving station on board a ship, and the station cf Fig. 1 may be sending out messages for several ships at the same time. Each of EiCii ship sets has its own local generator 17 which may be very small and may have a convenient frequency which may differ or be the same in the different sets and which need not bear any particular relation to the sending set except that'it should differ from the frequency of the wave to be received by an ultra-audible frequency. This fact permits a considerable latitude of adjustment. With the oscillator 17 operating, the antenna, 15 and circuit 16 are tuned to the wave to be received but as heretofore As example of l which may expointed out, these circuits will be practically equ-allv well tuned to other neighboring frequencies. By adjusting the tuning of circuits 19 and 20, however, the particular message intended for the set in question ma be individually received.

l ile this invention has been described as applied to radio communication, it will apparent that it may also be used in systems employing a line wire or wires in place of the antennae. Likewise the inve tion may be used in radio or wire systems in which apparatus other than signaling instruments are selectively operated at a receiving station or stations by impulses from a transmitting tation or stations. (5

The circuit arrangements, the description relating thereto, and the numerical values, it is to be understood,'are to be regarded as typical only of embodiments and uses which the invention may have, but they are not to be construed as in any way limiting the invention, the scope of which is defined in the appended claims.

at is claimed is: a

1. The method of radio signaling which comprises separately modulating each of a plurality of radio frequency waves in accordance with signals, transmitting said waves and receiving said waves simultaneously, producing a difference-frequency between each of said modulated Waves and another wave, and separating and converting the frequency of each of said difference-frequency waves to receive the signals in accordance with which said first mentioned waves have been modulated.

2. The method of receiving the signal component of each of a plurality of high frequency waves modulated in accordance with signalin waves which comprises receiving all 0 said modulated waves, coinbinin 'said modulated waves with an unmodu ated wave of a difi'erent frequency to produce the diderence frequency wave between each modulated wave and said unmodulated wave, separating said difi'erencefrequency waves and detecting them to reproduce the modulating waves.

3. The method of separately receivin aplurality of signal modulated waves having small frequency differences which comprises lowering the frequency of all of said waves by combining them with a locally produced wave to produce resultant modulated waves having comparatively widely different frequencies relative I0 0H6 another, separating said waves selectively, frequency of the separated waves by detection to produce their respective signal components.

4. A multiplex radio telephone system having transmitting and receiving stations comprising a plurality of sources of speechcontrolled radio frequency waves at the and converting the transmitting station frequency waves controlled at the receiving station, a circuit for causing all of sai waves to interact at the receiving station, and a separate circuit for receiving the speech component of each of the transmitted waves.

5. In combination, a plurality of sources of speech-controlled high frequency waves, a receiver for said waves comprising a source of high frequency waves, a circuit for combining waves produced at the receiver with each of the received waves to produce speech-controlled waves of frequencies lower than those of the received waves and a detector and receiver for the speech component of each wave so produced.

, 6. A receiver for separately receiving each of a plurality of high frequency modulated waves comprising a receivin terminal for said waves, a source of high frequency current at said terminal, a circuit 'for combining said high frequency current with the currents set up by all of said modulated waves to produce resultant modulated waves having frequency ratios widely different from unity, selective circuits for separating said resultant modulated waves and a detector and receiver for each of said resultant modulated waves.

7. In a signaling system employing transmitted high frequency waves having a frequency ratio one to another of nearly unity, each wave being modulated in accordance with signals, means for receiving the signal component of a plurality of said waves comand a source of radio prising a terminal for receivin all of said waves, a local source of big frequency waves at said terminal, a circuit for combinin a locally produced wave with the receive waves to produce resultant differencefrequencies havmg a frequency ratio one to another different from unity by an amount more than twice that by which the ratio of the correspondin transmitted waves differs from unity, a seective circuit for separating the desired resultant difference-freuency wave and a detector and a receiver or each di erence-frequency wave of said plurality.

'8. In radio signaling employing resonant wave collecting means, the method of separately receiving a plurality of sound modulated waves of difi'erent frequencies comprising simultaneously collecting the energy of said waves and reducing by means of locally generated waves the frequencies of the received waves by an arbitrary amount inde pendent of said wave collecting means to increase the the frequency characteristics of percentage frequency difference between the waves to an extent permitting their ready separation by filtering circuits, separating the waves of frequencies thus reduced into separate channels, and detecting the selected waves to separately produce the sound signals individual thereto. 4

In witness whereof I hereunto subscribe my name this 26th day of September, A. D. 1919.

RAYMOND A. HEISING. 

